硅中Jahn-Teller畸变的磷-空位复合缺陷的电子结构

本文采用扩展的缺陷势,利用一个紧束缚的Koster-Slater格林函数方法,确定了磷-空位缺陷的波函数为深能级E的函数,以深能级的实验值为输入参数,得到的波函数定量地描述了EPR和ENDOR实验资料,特别是,理论给出空位的四个近邻原子上的超精细相互作用常数α和b,同实验符合得很好。 关键词：     

环电流磁矩进动的演示与分析

给出一种可有效地演示电子轨道磁矩在外磁场中的进动规律的环电流陀螺,以及演示涡流存在的导体陀螺,并给出了相应分析．     

PbWO4晶体中铅空位相关的色心模型

使用密度泛函缀加平面波法,按照能量最低原理采用共轭梯度方法对几种含铅空位和不含铅空位的钨酸铅晶体进行结构优化处理,计算了铅空位周围晶格的弛豫,得到铅空位周围的晶格结构,同时对计算结果进行了讨论;在得到几何优化结构的基础上,利用相对论性密度泛函离散变分法进一步计算了几种钨酸铅晶体结构的电子态密度.计算结果表明:1)铅空位周围的晶格驰豫的结果使铅空位的局部电负性减弱.2)Pb 6s态的能级位于离价带顶10eV左右,说明Pb 6s态上的电子很难再失去,所以在钨酸铅中不太可能存在Pb3+或Pb4+.3)价带顶主要由O的2p态占居,氧的2p态最容易失去电子.4)铅空位周围的可能形成的色心是VF--VK+缔合色心.     

化合物SmCo5的电子结构、自旋和轨道磁矩及其交换作用分析

用自旋极化的MS-Xα方法研究了稀土-过渡族化合物SmCo5的电子态密度、自旋能级劈裂及原子磁矩.研究结果显示,由于化合物中Sm-Co间的轨道杂化效应,使Sm原子原来的5d0空轨道上占据了少量5d电子.由于Co(3d)-Sm(5d)电子间的直接交换作用,导致了Sm-Co间的磁性交换耦合,这是化合物中形成Sm-Co铁磁性长程序的一个重要原因.在SmCo5化合物中存在6个能级呈现负交换耦合,导致了SmCo5化合物的居里温度(与金属钴相比)明显下降.还研究了化合物中2c和3g晶位Co的自旋磁矩和轨道磁矩,发现Co(2c)晶位的自旋磁矩、轨道磁矩及冻结部分均略大于Co(3g)晶位,所以2c晶位的L-S耦合强度应略大于3g晶位.因此,2c晶位对SmCo5磁晶各向异性的影响也应大于3g晶位.但Co(2c)未被冻结的轨道磁矩却略小于Co(3g),所以两种晶位对磁晶各向异性的贡献大小之差别不应太大.考虑到4f电子的局域性和化合物中轨道杂化效应所导致的Sm(5d0)空轨道上占据了少量5d电子,可以得到Sm原子磁矩为1.29μB,与顺磁盐中Sm3+磁矩实验值(1.32-1.63uB)及金属中Sm原子磁矩实验值(1.74μB)基本符合.     

探测环绕碳纳米管运动电子的轨道磁矩

环绕碳纳米管(CNT)运动的传导电子应轨道磁矩.轨道磁矩影响CNT的磁化率以及磁电阻等物性,或者说,影响CNT在外场下的电子能态.不过,在已往的实验中上述轨道磁矩从未被探测过.最近,来自美国康奈尔大学原子和固态物理实验室的Minot等以他们的新实验证明:环绕CNT壁作轨道运动的电子,其轨道磁矩的幅值大致与理论预言相符,它等于单电子环行所产生的电流与环路面积的乘积.假定电子的环行速度是vF,CNT的直径是D ,则电子的轨道磁矩μorb=DevF/4 ,其中e是电子电荷.当一根小能隙的CNT悬挂在源极和漏极之间,便形成了一个量子点.量子点中处于导…     

传导电子与声子的相互作用对局域磁矩的影响

本文在Anderson提出的s-d混合模型中,考虑了传导电子与声子的相互作用(简写成EPI)和传导电子与d电子之间的库仑相互作用。主要讨论了EPI对局域磁矩的存在和大小的影响。     

氧空位浓度对ZnO电子结构和吸收光谱影响的研究

目前,氧空位对ZnO形成杂质能级的研究结果存在相反的结论,深杂质能级和浅杂质能级两种实验结果均有文献报道,并且,在实验中高温加热的条件下,氧空位体系ZnO中导带自由电子增加的来源认识不足.为了解决此问题,本文采用密度泛函理论框架下的第一性原理平面波超软赝势方法,建立了纯的与两种不同氧空位浓度ZnO超胞模型,分别对模型进行了几何结构优化、态密度分布、能带分布、布居值和差分电荷密度的计算.结果表明,氧空位浓度越大,系统能量越上升、稳定性越下降、形成能越高、氧空位越难、导带越向低能方向移动、电子跃迁宽度越减小、吸收光谱越红移.这对设计制备新型氧空位ZnO体系光学器件有一定的理论指导作用.     

原子簇La8-xBaxCuO6的原子磁矩和自旋极化的电子结构研究

利用MS-Xα方法研究了化合物La2-yBayCuO4的原子磁矩和自旋极化的电子结构.理论计算得到母相氧化物La2CuO4的Cu原子磁矩为0.37μB,与实验值0.48±0.15μB基本一致. 研究结果显示, 由于Ba原子对部分La的替代,使构成化合物的基本原子簇La8-xBaxCuO6的点群对称性降低,分子轨道简并度解除,轨道杂化效应增强,减弱了氧化物的(准)二维特性,导致Cu-O层与其近邻原子层的耦合增强,因此影响了原子层间的电荷迁移方向,对Cu-O层中载流子的性质有重要影响. 由于Ba掺杂在化合物中产生的空穴,不仅进入O格点,也同时进入Cu格点,对Cu-O层上Cu和O原子价态、磁矩以及电子态密度分布有重要影响. 研究结果认为,由于掺杂产生的空穴对化合物超导电性的影响具有两面性:初期掺杂有利于产生超导电性;当掺杂较多时抑制超导电性. 这是导致La214体系的超导转变温度Tc随掺杂量y的变化(即Tc-y拱形曲线)的一个重要原因.     

δ-Pu空位缺陷的密度泛函理论计算

采用密度泛函理论框架下的平面波赝势方法,计算了空位缺陷对δ-Pu结构稳定性和电子结构的影响.建立了1×1×2、2×2×1和2×2×2 3种晶胞中的空位缺陷模型,分别计算了其晶格常数、空位形成能、结合能、态密度、电荷密度分布以及Mulliken电荷布居.计算结果表明:空位缺陷在δ-Pu中不能稳定存在,且会导致晶体的整体结构稳定性降低.在3种缺陷模型中,2×2×1的模型空位稳定性和结构稳定性都相对更强;空位导致δ-Pu电子的局域性降低,电子相互作用也发生了一定的变化,其中2×2×1的模型中与空位最邻近的Pu原子发生了明显的sp杂化,这在一定程度上说明了其稳定性最强的原因;空位引起电荷由近空位端向近Pu端转移,且导致最邻近Pu原子失去电子,而这部分电子主要由6p轨道贡献.     

稀土元素Ce的特性与4f电子局域磁矩

本文考虑到电声子相互作用以及4f电子与传导电子相互作用的贡献,对稀土Ce中伴随γ-α相变时所发生的变价现象与磁性等物理特性的关系作了研究,分析了当温度、压强、化合价等变化时稀土金属中的电子行为。     

电矩张量与旋转带电体的磁矩

基于旋转带电体的磁矩与刚体转动惯量之间的类比关系,引入带电体的一个不同于电四极矩的电矩张量的概念,进而引入标量电矩二次曲面及电矩主轴的概念,借助正交变换及电矩张量矩阵的本征值理论,推导出沿任意方向定轴旋转带电体的磁矩的计算公式及电矩张量的若干性质,并举例说明.     

磁场及磁矩的测量实验

对地磁水平分量测量实验加以改进,将其扩充为能够测量亥姆霍兹线圈磁场分布和磁针的转动惯量以及磁针磁矩的实验.使其成为一个综合性较强,适用于开展研究性实验的项目.     

Majorana neutrino transition magnetic moment in a variant of Zee model with horizontal symmetry

A SU(2) _H symmetric variant of Zee model of lepton flavor violation is presented and is shown to lead to neutrino transition magnetic moment of the order required to explain the solar neutrino deficit and the possible anticorrelation of solar neutrino flux with sunspot activity via VVO mechanism. The use of horizontal symmetry leads to totally degenerate neutrino states which may be combined to form a ZKM Dirac neutrino with naturally small mass.     

Study of electronic and magnetic properties of MnS layers

<正>Self-consistent ab initio calculations,based on the density functional theory(DFT) and using the full potential linear augmented plane wave(FLAPW) method,are performed to investigate both electronic and magnetic properties of the MnS layers.Polarized spin and spin-orbit coupling are included in the calculations within the framework of the antiferromagnetic state between two adjacent Mn layers.Magnetic moments considered to lie along axes are computed. Obtained data from ab initio calculations are used as input data for the high temperature series expansion(HTSE) calculations to compute other magnetic parameters.The zero-field high temperature static susceptibility series of the spin-4.39 nearest-neighbour Heisenberg model on centred face cubic(FCC) and lattices is thoroughly analysed by a power series coherent anomaly method(CAM).The exchange interactions between the magnetic atoms,the Neel temperature,and the critical exponent associated with the magnetic susceptibility are obtained for the MnS layer.     

Magnetic correction to the anomalous magnetic moment of electrons

We investigate the leading order correction of anomalous magnetic moment (AMM) to electrons in a weak magnetic field and find that the magnetic correction is negative and magnetic field dependent, indicating a magnetic catalysis effect for the electron gas. In the laboratory, to measure the g − 2, the magnitude of the magnetic field B is several T, and correspondingly the magnetic correction to the AMM of electron/muon is around 10⁻³⁴/10⁻⁴², therefore the magnetic correction can be safely neglected in the current measurement. However, when the magnitude of the magnetic field strength is comparable with the electron mass, the magnetic correction of the electron's AMM will become considerable. This general magnetic correction to the charged fermion's AMM can be extended to study quantum chromodynamic matter under a strong magnetic field.     

运动介质的电偶极矩与磁矩

在推导出介质的极化强度与磁化强度的坐标变换公式的基础上,分析导出了运动介质的电偶极矩与磁矩.     

The anomalous magnetic moment of the electron

The value of the electron's magnetic moment is a fundamental quantity in physics. Its deviation from the value expected from Dirac theory has given enormous impetus to the field of quantum theory and especially to quantum electrodynamics (QED) as the relativistic quantum field theory of electrodynamics. In fact, the measured values both for free and for bound electrons are explained by corresponding QED calculations on the part per trillion and part per billion level of accuracy, respectively. This agreement is amongst the best known in physics today. In turn, it allows highly precise determinations of related fundamental constants like the fine structure constant α or the electron mass. The present article discusses the application of the continuous Stern–Gerlach effect to the precise measurement of magnetic moments, especially of the electron bound in highly charged ions and possible tests of calculations in the framework of QED of bound states. Also, a test of QED in a more general approach by the comparison of values for the fine structure constant derived from different measurements, will be discussed.     

On the interpretation of the electron anomalous magnetic moment

Guided by a Compton-sized model, we demonstrate that: (a) the magnetic self-energy of the electron, as estimated initially by Rasetti and Fermi, can be directly related to both the sign and the magnitude of the electron anomalous magnetic moment; and (b) the classical expression for the magnetic self-energy of the electron exhibits the same characteristic logarithmic divergence that occurs in QED. This electron model quantitatively reproduces the spin, magnetic moment, and gyromagnetic ratio of the electron, correct to first order in = e² /c. It also relates the quantum-mechanical spin projection angle to the vanishing of the electric quadrupole moment, and it is capable of reproducing point-like scattering behavior.     

A simple method to estimate the magnetic moment of magnetic micro-particles

Micro-particles in suspension in a fluid are an example of a very low Reynolds number problem. In this case, no inertial effects are observed. Magnetic micro-particles with magnetic moment m, suspended in a fluid orient to applied external magnetic fields B due to the interaction between the field and the magnetic moment. In this work, we present a simple method to estimate the total magnetic moment of magnetic micro-organisms. The method is based on the application of an external oscillating magnetic field in the sites where the micro-organisms are. In this case, it is possible to obtain theoretically the solution of the equation of motion (rotation of the organism and its trajectory). The solution is a transcendental equation relating the orientation angle and m and can be solved by numerical methods. Changing the frequency and/or the field intensity, it is possible to obtain a situation in which the crystal rotates uninterruptedly (a resonance regime). This condition is related to the applied field intensity, to the frequency, to the medium viscosity, to the crystal dimension, and to the micro-crystal magnetic moment m. The method can be used to estimate the total cellular magnetic moment of magnetic micro-particles.     

Nuclear magnetic moment: Relativistic mean field description

Valence nucleon effective mass, which is almost constant, is proposed within the relativistic mean field theories of finite nuclei (closed shell ± one nucleon). It acquires a slight spin-orbit splitting due to relativistic effects. The relativistic Dirac magnetic moment is rewritten analytically in terms of angular momentum-Pauli spin coupled states and the effective mass. Introducing the nucleon effective charge, the iso-scalar and iso-vector corrections to the magnetic moment operator are extracted from the overall one parameter fit of the measured and the calculated values. The calculated values of magnetic moments are in overall fair agreement with the experiment as well as with the other detailed microscopic calculations.